Precious metal rupture disc



United States Patent Ofice 2,947,623 Patented Aug. 2, 1960 PRECIOUS METAL RUPTURE DISC No Drawing. Filed May 1, 1953, Ser. No. 133,470

3 Claims. c1. 15-165 The present invention deals with a rupture disc and more particularly to an alloy for a rupture disc adapted to be ruptured by fluid pressure when the fluid pressure cxceeds a predetermined value.

Storage containers containing fluid, or fluid chambers containing, e.g. pressurized gases or liquids are usually provided with a safety device for effecting a pressure release to safeguard against the buildup of excessive gas or liquid pressures which become potentially dangerous. A convenient safety device comprises a structure in the form of a valve which contains a frangible or rupturable diaphragm or disc. While a rupture diaphragm or disc may be composed of various metals or metal alloys such as copper, bronze, silver, gold, aluminum, etc.,' and alloys thereof, discs made from precious metals or precious metal alloys are advantageous when the container contains corrosive gases. Under corrosive conditions it has been found that discs or diaphragms made from substantially pure gold or substantially pure silver are advantageous in providing desirable rupture characteristics. However, the disadvantage in the use of such substantially pure metals is that they inherently contain very small or minute amounts of metal impurities and the impurities vary as to composition and amount. For example, it has been found that substantially pure gold and silver usually contain a variation as to the' amount and the nature of other metal impurities. In such case it is extremely difiicult to control the metals to provide uniform rupture pressures.

It is an object of this invention to provide an alloy for rupture discs which provides uniform rupture pressures. It is another object of this invention to provide an alloy for mpture discs which provides uniform and substantially low pressure rupture characteristics. It is a further object of the present invention to provide alloys for rupture discs which have rupture characteristics of pure metals. It is a still further object of this invention to provide a rupture disc composed essentially of gold or silver and having controlled rupture characteristics. Other objects and advantages of the invention will be apparent fi'om the description hereinafter following.

The present invention relates to alloys for the manufacture of rupture discsand which alloys contain inherent minute amounts of impurity metals including at least two of the metals platinum, iridium, palladium, rhodium, ruthenium, copper, iron, nickel, manganese, calcium, lead, tin, zinc, and antimony. A certain small amount of such impurity metals is in fact favorable because they tend to restrict grain growth. However, even in minute amountsfia variation of the impurity metal content between two pieces of metal stock will render a disc or diaphragm made therefrom Variable as to rupture pressure. It has been found, in accordance with this invention, that by adding from 0.1% up to less than 1% of a metal selected from the impurity metals, which amount is more or greater than all non-selected impurity metals combined, that such addition will render the other impurity metals inelfective to vary the rupture characteristics of the disc or diaphragm. In the case of a substantially pure gold alloy containing minute amounts of impurity metals, it has been found advantageous to incorporate from 0.1% up to less than 1% of palladium to the gold.

The term impurity metals e.g. as applied to gold, refers to minute amounts of residual metals other than gold contained in commercially or chemically pure gold.

When 1% or more of an additive metal is employed it is very difficult to obtain the lowest possible rupture pressure characteristics for a given metal and given set of parameters, e.g. thickness and working diameter of the rupture disc. In such cases the rupture disc or diaphragm no longer resembles the rupture character of, e.g. fine gold Within a desirable tolerance.

By adding to substantially pure gold or silver containing impurity metals, palladium in an amount of up to less than 1% which amount is greater than all minute amounts of impurity metals combined, the rupture disc alloy is substantially standardized for the provision of reproducible rupture characteristics. It is important that the additive metal is such that it will go into solid solution with the main metal content, e.g. gold or silver, and will not alfect the nobility of such metal.

The alloys herein contemplated are essentially composed of from 99.0% to 99.9% of a metal such as gold or silver with from 0.1% to less than 1% of one of the impurity metals above listed. For example, a satisfactory alloy consists of 99.5% gold, 0.45 palladium and 0.05 impurity metals.

A 200 ounce bar of such composition was rolled to a sheet having a thickness of 0.0212 inch and three discs of .5 inch working diameter were blanked from the sheet. Under test conditions, the discs ruptured at 2,975, 3,075, and 3,075 lbs/sq. in. against a rated rupture pressure of 3,000 lbs/sq. in.

While gold and silver has been specifically mentioned as preferable metals for rupture discs or diaphragms, other substantially pure precious metals i.-e. platinum or palladium or base metals such as copper and aluminum may be used, provided an additive metal in the range hereinabove set forth is employed to standardize such other metals.

While specific rupture disc or rupture diaphragm impurity metals have been mentioned, various modifications of the rupture disc or diaphragm metal alloy are contemplated within the scope of the appended claims.

What is claimed is:

1. A method of protecting fluid containers from rupture comprising utilization of a rupture disc in said container composed of an alloy from the group consisting of gold and silver in amounts of from 99.0 to 99.9 weight percent, the balance composed of at least two metals taken from the group consisting of platinum, iridium, palladium, rhodium, ruthenium, copper, iron, nickel, calcium, manganese, lead, tin, zinc and antimony, one metal of said group being present in an amount of from 0.1 to less than 1 weight percent of the alloy, the amount of said one metal being greater than the combined amount of all other metals of said group.

2. An alloy according to' claim 1, comprising 99.5 percent gold, 0.45 percent palladium and 0.05 percent of said other metal.

3. A methdod according to claim 1, wherein the said alloy consists of gold as the base metal, and palladium being one of the selected metals comprising the balance of the alloy.

References Cited in the file of this patent UNITED STATES PATENTS 2,440,691 Jira May 4, 1948 

1. A METHOD PROTECTING FLUID CONTAINERS FROM RUPTURE COMPRISING UTILIZATION OF A RUPTURE DISC IN SAID CONTAINER COMPOSED OF AN ALLOY FROM THE GROUP CONSISTING OF GOLD AND SILVER IN AMOUNTS OF FROM 99.0 TO 99.9 WEIGHT PERCENT, THE BALANCE COMPOSED OF AT LEAST TWO METALS TAKEN FROM THE GROUP CONSISTING OF PLATINUM, IRIDIUM, PALLADIUM, RHODIUM, RUTHENIUM, COPPER, IRON, NICKEL, CALCIUM, MANGANESE, LEAD, TIN, ZINC AND ANTIMONY, ONE METAL OF SAID GROUP BEING PRESENT IN AN AMOUNT OF FROM 0.1 TO LESS THAN 1 WEIGHT PERCENT OF THE ALLOY, THE AMOUNT OF SAID ONE METAL BEING GREATER THAN THE COMBINED AMOUNT OF ALL OTHER METALS OF SAID GROUP. 